CN1084986A - The data on the multi-format data bus and the exchange of clock line - Google Patents

Abstract

A kind of signal processing system that comprises the bus slave of serial data bus, (SERBUS1 is SERBUS2) in order to be coupled to different auxiliary processor (160,150) on the main processing controller (CONTROL μ C) to have first and second bus lines.Each additional device need be used more than one data bus protocol.The clock of the additional device of a protocol-specific and data terminal connect first and second bus lines respectively.Agreement during processor controls change to be used to be producing required bus transfer, and changes the work of two bus lines in order to avoid some bus collision situation during conversion between each bus protocol.

Description

The data on the multi-format data bus and the exchange of clock line

The signal processing system of the bus slave system of the present invention relates to.Signal processing system can adopt by the various integrated circuit of one or more control microcomputers (μ C) control and realize.Communication between the difference in functionality relates generally to for example data bus of line data bus one class.For the signal processing system that makes bus slave has the function of all expections, often need the signal processing integrated circuit (IC) that adopts different manufacturing firms to produce.But it is several that the communication protocol that each manufacturing firm supports often has, and have nothing in common with each other.What for example, Philips and ITT Corp. supported respectively is to be called Inter IC(IIC or I2C) and the Intermetall(IM) bus standard of standard.

The signal that the form that adopts multiple communication protocol that the integrated circuit (IC) of a protocol-specific is understood mistakenly on the individual data bus to press different agreement is worked out.Bus standard stipulated expression information begin and finish the signal mode of situation, device address and with the information data of each equipment of bus coupling.For example, for a signal, in the particular state process at an other signal, the particular conversion that occurs on this signal is expression " information begins " for the iic bus standard.The signal waveform that meets the IM bus standard and produce may can produce the situation of expression " initial information " concerning the iic bus standard accidentally.If IM and IIC equipment are all received a certain bus, then IIC equipment can be encouraged unintentionally in IM format information process.So two equipment will require to communicate on this bus simultaneously, thereby make the transmission in the continuation can not normally carry out and make system's cisco unity malfunction.

Data value and timing are depended in the appearance of the conflict on above-mentioned bus is used.Therefore, any maloperation that these conflict and system takes place afterwards all is intermittent.System tested to identify those data patterns that to be avoided for avoiding a conflict.Though it is bothersome time-consuming that all presumable data patterns are tested, and has reliable performance for guaranteeing system, still be necessary to carry out.In addition, device type changes or also needs to repeat this test when adding new equipment on bus.

One aspect of the present invention is recognized the problems referred to above, relates to the equipment that addresses the above problem on the other hand.One aspect of the present invention relates to a kind of data bus, and this data bus has first and second bus lines, respectively in order to first and second data processing devices are coupled on the control device.First data processing device has clock terminal and data terminal, is coupled to respectively on first and second bus lines.Second data processing device has clock terminal and data terminal, is coupled to respectively on second and first bus line.Control device clocking and data-signal on first and second bus lines respectively in the first working method process do not influence the work of second data processing device with the work of controlling first data processing device.Control device clocking and data-signal on second and first bus line respectively in the second working method process do not influence the work of first data processing device with the work of controlling second data processing device.

Referring to the accompanying drawing content that the present invention may be better understood.In the accompanying drawing:

Fig. 1 shows the signal processing system block scheme of the bus slave of a part that comprises first aspect present invention;

Figure 1A shows that a part of block scheme that shows the bus collision problem that the present invention mentions in the signal processing system of bus slave;

Fig. 2,3,4A and 4B show the signal waveform of the working condition that helps to understand system shown in Fig. 1.

In more detail, Fig. 1 shows the part of the signal processing system of bus slave, and this part comprises control microcomputer (μ C) 100 and device 150 and 160.Serial data bus is made up of signal bus SERBUS1, SERBUS2 and SERBUS3, and it is coupled to μ C100 on device 150 and 160.Control μ C100 can be the microprocessor that resembles MC68HC05 one class of motorola inc's product.Device 150 and 160 is one or more signals or the data processing devices that can be digital integrated circuit or Analogous Integrated Electronic Circuits.The work of these devices is the IC(IIC that adopt device 150 by serial data bus) Intermetall(IM of bus protocol and device 160) bus protocol controls.For example, in the video signal preprocessor that resembles CTC-169 colour television set chassis one class that Thomson consumer-elcetronics devices company produces, device 150 is to resemble the Microchip24CO2(electrically erasable read-only memory), the tuning processor of Motorola MC44802() and Philips 8444(D/A (DAC)) integrated circuit of a class.In the same example of video signal preprocessor, device 160 is to resemble Thomson 1A68109(Proscan processor), Thomson 1A68106(stereo processor) and Thomson 1A68105(picture-in-picture (PIP) processor) integrated circuit of a class.

Fig. 2 shows the bus signals form of IIC and IM bus protocol.As shown in Fig. 2 A, the communication in the IIC form needs clock signal SCL and data-signal SDA.When iic bus suspends the not time spent, signal SCL and SDA should be in the state of logical one.During signal SCL is in logical one and when signal SDA enters logical zero, produce the situation of " information begins "." start bit " of 8 address of devices just arranged and with the affirmation position that acknowledges receipt of this address after the beginning situation.After the Address Confirmation position then is 8 (1 byte) data and data validation position.Address in the IIC form and data are to transmit highest significant position (MSB) earlier when transmission.Other data byte is together with the appearance of corresponding data validation position, can be " information stops " or " end of transmission (EOT) " (EOT) before situation makes end-of-message.The EOT situation appears at as SCL and is in logical one and signal SDA when go up producing logical zero to the conversion of logical one.

IM bus protocol shown in Fig. 2 B needs three signal: enabling signal IDENT, clock signal C LOCK and data-signal DATA.The IM bus protocol is such expression " information begins ": signal IDENT converted logical zero to before this, then was that signal CLOCK converts logical zero to." information begins " is one 8 bit address and 8 bit data afterwards.Address in the IM form and data are transmitted least significant bit (LSB) (LSB) earlier when transmission.After the transmission of all address bits, signal IDENT changes logical one into, to impel the IM device that respectively is attached on the bus address of being transmitted and the address of device is compared.Wherein do not comprise and confirm the position.Some data bytes in addition can be followed after initial byte." information stops " or EOT represent with the pulse on the signal IDENT.

In system shown in Figure 1, resemble signal IDENT, the CLOCK of IM bus protocol IC of device 160 1 classes among Fig. 1 and DATA and all be coupled to respectively on signal SERBUS3, the SERBUS1 and SERBUS2 from the μ C100 among Fig. 1, it seems that this arrangement be that signal SERBUS1 and SERBUS2 are decided to be clock signal and data-signal respectively.Therefore, the signal SCL and the SDA(that obviously resemble the IIC agreement device of device 150 1 classes are respectively clock and data) just receive serial bus signal SERBUS1 and SERBUS2 respectively, as shown in Figure 1A.But according to characteristics of the present invention, signal SCL and SDA system are coupled to respectively on signal SERBUS2 and the SERBUS1, as shown in fig. 1.This unusual arrangement has advantageously prevented the bus collision problem, will speak of below.

In the embodiment shown in fig. 1, control μ C100 produces the information of IIC and IM form, so as for the usefulness of IIC device (for example device 150) and IM device (for example device 160) communication.Control μ C100 by employing be called " shift register " mode and " position is impacted " (bit-bang) two kinds of working methods of mode finish this program.The shift register mode is in order to produce the IM format signal, and impact mode in position is in order to produce the IIC format signal.

When the shift register mode, IM format string line data (the IM signal DATA on the bus line SERBUS2) adopts 8 bit shift register 112 among Fig. 1 and produces.Shift register 112 is dedicated serial communication interface (SCI) 110 parts in μ C100.Can see that from Fig. 2 B the composition of each 8 bit data value of IM formatted data signal is consistent.Therefore, 8 bit shift register can produce 8 bit serial data-signals of IM form effectively.For example, when from μ C100 when the device that resembles device 160 1 classes transmits, μ C100 deposits 8 bit address in 8 bit shift register 112, and everybody is moved on on the bus line SERBUS2 by signal SDAT, to produce 8 bit address parts of IM format information.Just 8 bit data bytes are deposited in the shift register 12 after the transport address, and 8 bit data are moved on on the bus line SERBUS2.

It is irregular waveform that the waveform that Fig. 2 A illustrates iic bus protocol requirement data-signal (signal SDA) is compared with the waveform of IM agreement.More particularly, require the start bit and the affirmation position of 8 bit address or data.The capacity of shift register 112 is limited to 8, and this has hindered, and the IIC data-signal is desired to produce irregular sequence effectively.Therefore 9 bit sequences produce in μ C100 by the software program of carrying out in " position is impacted " mode process.The position blasting operation adopts internal register and the data management function of μ C100, thereby each ground produces desired serial bit pattern on signal BDAT.For example, signal BDAT can be coupled on the position of internal register.The instruction of depositing, being shifted and fulfiling logical operation of the content of internal register all be can be used to change the value of signal BDAT, so that the desired serial data sequence that has to be provided.

Should be noted that impact mode in position can both be applicable to that the IM form also was applicable to the serial data signal of IIC form with producing.But much higher during the severals speed ratios position blasting operation when shift register 112 produces serial data signals, this is to carry out due to the delay because contain software in the shock treatment.Therefore, preferably adopt the shift register mode whenever possible.

Among Fig. 1, ternary MUX120 and 130 usefulness for the conversion between shift register working method and the position impact working method are housed among the μ C100.The conversion of MUX is controlled by the control signal (not shown in figure 1) that is coupled on MUX120 and the MUX130 by μ C100.Control signal impels MUX120 and MUX130 " A " input end by MUX120 and 130 in serial-shift mode process to be coupled to respectively on serial bus line SERBUS1 and the SERBUS2 from signal SCLK and the SDAT of SCI110.So on serial bus line SERBUS1 and SERBUS2, produce IM bus signals CLOCK and the DATA that corresponds respectively to signal SCLK and SDAT respectively.In the impact mode process on the throne, signal SDAT and BCLK produce in μ C100, and are coupled to respectively on serial bus line SERBUS1 and the SERBUS2 by " B " input end of MUX120 and MUX130.So produce iic bus signal SDA and the SCL that corresponds respectively to signal SDAT and BCLK on serial bus line SERBUS1 and the SEBUS2 respectively.Bus line SERBUS3 only is the enabling signal IDENT of IM form device, and working method is not changed when changing.

The ternary characteristics of MUX120 and MUX130 make can two-way operation on bus line SERBUS1 and SERBUS2.Whether control μ C100 relates to data according to the particular serial bus operation is write a certain device or data are read in the operation of controlling the ternary characteristics of MUX120 and 130 the μ C100 from a certain device from μ C100.

As shown in Fig. 1 and following table 1, the action of MUX120 and MUX130 impels the function of bus line SERBUS1 and SERBUS2 reversing when serial-shift mode (IM format information) conversion puts impact mode (IIC format information) in place.

Table 1

SERBUS 1 SERBUS 2

Mode/form is coupled to Function Coupling to function

Shift register/IM SCLK clock SDAT data

Position impact/IIC BDAT data BCLK clock

In general, the effect of bus line in signal processing system can not changed between clock and data function.After the relevant detailed description of above-mentioned bus collision problem possible cause, can understand the advantageous property of above-mentioned the sort of scheme better below the research.

For explanation bus collision situation, will discuss with regard to Figure 1A below.Among Figure 1A, the signal SCL of IIC device and the signal CLOCK of IM device are received serial bus line SERBUS1, and signal SDA and DATA are received serial bus line SERBUS2.Therefore, bus line SERBUS1 always provides clock signal, and bus line SERBUS2 always provides data-signal.As a result, the scheme of Figure 1A also comprise impact a signal BDAT(both who produces from the SDAT of SCI110 and position and be coupled to MUX130) and signal SCLK and BCLK(both meet MUX120).

Fig. 3 shows the bus collision problem that may occur in the system shown in Figure 1A when transmitting the IM form after transmission IIC form.A sequence transmission of being made up of IM transmission, the transmission of IIC form and the transmission of another IM form has been shown among Fig. 3.Between an IM transmission period, signal SDAT is coupled on the SERBUS2, and its value shifts out outside the shift register 112.Between next IIC transmission period, MUX130 is coupled to signal BDAT on the bus line SERBUS2, and synchronous signal SDAT keeps originally shifting out the last value outside the shift register 21.In the example of Fig. 3, the last value of signal SDAT is a logical zero.In the IIC transmission at the end, the value of signal BDAT is set to logical one, thereby produces the EOT situation, and makes bus enter the state that wouldn't work.

When IM transmission afterwards began, MUX130 was coupled to signal SDAT on the bus line SERBUS2 through conversion.The conversion of MUX130 can impel serial bus line SERBUS2 to enter the logical zero value of the signal SDAT that transmits from a last IM from the logical one that suspends off position.Unequal signal delay may make the timing of the switching time of bus line SERBUS2 from the logical one to the logical zero change with the variation on the bus line SERBUS1 between bus line SERUS1 and the SERBUS2.The dash area of signal SERBUS2 shows this switching time of variation regularly among Fig. 3.Unequal delay may for example unequal dead resistance and capacity effect cause.These parasitic elements are represented with resistor R1 and R2 and capacitor C1 and C2 in Fig. 1 and 1A.Resistor R 3 is device works (pullup device) that the IIC data line may need, because the bus line driver in the IIC device generally is the structure of open collector.The general resistance of R1 and R3 is respectively 1 kilo-ohm and 10 kilo-ohms.

Take place when signal SERBUS1 is in logical one if change logical zero on the bus line SERBUS2, then the IIC device can produce the false start situation between the IM transmission period, as shown in Figure 3.Like this, IIC device and IM device all detect the starting situation.Said different (IM transmits LSB earlier, and IIC then transmits MSB earlier) of the significance bit of the bits of serial data of IIC transmission and IM transmission above.Even therefore IM device and IIC device are not assigned to same address, the address information that IM device desire is used when planning to carry out the IM transmission also is effective address concerning the IIC device.So false IIC starting situation and effective I M starting situation may work to IIC device and IM device simultaneously.The IIC device that works is just used and is confirmed that thereby the position goes to respond effective address and may destroy the IM data-signal.

By will be in addition converse according to the action function of the bus line of characteristics shown in above-mentioned and Fig. 1 of the present invention, so, the MUX conversion that when IM transmission beginning signal SDAT is added on the bus line SERBUS2 will impel consequent any signal SERBUS2 conversion to be coupled to the input end of clock (SCL) of IIC device as shown in fig. 1, rather than be coupled to the data input pin (SDA) among Figure 1A.False start situation shown in Fig. 3 so just can not take place.

Because the reverse of the function of bus line can produce similar problem.For example, referring to Fig. 3, if first address bit of IM address of devices or a plurality of address bit are in logical one in the 2nd IM transmission, when then the IM clock signal C LOCK on the bus SERBUS1 changed, the IM data-signal DATA on the bus line SERBUS2 can still be in logical one.Therefore, (on the bus line SERBUS2) IIC clock signal SCL still is in logical one at (on the bus line SERBUS1) IIC data-signal SDA when changing.This situation has produced the IIC starting situation of a sequence.Yet because the IM clock signal on the SERBUS1 turns back to logical one at once after being transformed into logical zero at every turn, thereby the situation of at every turn starting is that IIC stops situation or EOT afterwards with that.The IIC device can not receive 8 complete bit address as a result, thereby can not produce the vacation affirmation position that causes destroying the IM transmission.

Also can produce bus collision when repeating to transmit the information of IM form.Fig. 4 A illustrate IM format information finish (with transmit " stopping " or " end " (EOT) pulse represent situation about beginning with another IM information.When an end of message (EOM), IM signal CLOCK and DATA(bus line SERBUS1 and the SERBUS2 in Figure 1A) be forced to change over to the logical one of inoperative state.As shown in Fig. 4 A, signal DATA begins to change over to logical one after signal CLOCK has changed logical one over to.Time delay between the conversion of signal CLOCK shown in Fig. 4 A and DATA may be caused by above-mentioned unequal parasitism on the serial bus line is loaded with.After logical transition threshold value VT, in fact signal DATA is in logical one.But momentary signal (for example clutter) may be worked as signal DATA and be finished its conversion that changes logical one over to passing threshold VT spike of generation negative sense in signal DATA afterwards before.Therefore signal DATA may show as the pulse of trend logical zero when signal CLICK is in logical one.If this duration of pulse long enough and system connect, then can produce false IIC starting situation as Figure 1A.

Fig. 4 B is illustrated in another possible cause of the bus collision that may occur in the system that connects in the process of the IM format information that a sequence occurs as Figure 1A.System shown in Fig. 1 can design to such an extent that make any " forcing " state (for example forcing the state for logical one) that transmits at the end the signal CLOCK and DATA at IM at the end be released as elicit illness state (high impedance) in the IM transmission, in case this anancastia is disturbed later bus transfer.Yet will impel the variation of signal DATA value slower at this elicit illness state situation leakage current, shown in Fig. 4 B.If the time long enough that high impedance status continues, signal DATA(bus line SERBUS2) variation of value may intersect with switching threshold VT, and the state with signal DATA changes to logical zero effectively.If signal CLOCK(bus line SERBUS1 when state changes) be in logical one, then in the system of wiring such as Fig. 1, there is false IIC starting situation.

Potential problems shown in Fig. 4 A and the 4B are solved by the function according to the conversion bus line of characteristics of the present invention.As above such in the face of the explanation that Fig. 3 did, the function of changing bus line resembling among Fig. 1 can prevent that the signal SDA of IIC device from going up the above-mentioned false conversion of generation, rise and state false conversion thereby prevent to produce in these cases false IIC, thereby prevent to produce in these cases false II starting situation.

Claims (3)

1, a kind of equipment comprises:

A data bus is made up of first bus line (SERBUS1) and second bus line (SERBUS2);

First device (160) and second device (150) are coupled on the described data bus, for the usefulness according to the signal Processing data on the described data bus; With

Control device (CONTROL μ C, 110) is coupled to described data bus, is used to provide signal to control the data processing that described first and second devices carry out; It is characterized in that;

Described first device has an input end of clock (CLOCK) and data input pin (DATA), is coupled to respectively on described first and second bus lines, in order to come deal with data according to clock and the data-signal received at described clock and data input pin;

Described second device has an input end of clock (SCL) and a data input end (SDA), is coupled to respectively on described second and first bus line, in order to come deal with data according to clock and the data-signal received at described clock and data input pin; And

Described control device during first working method on described first bus line clocking (IMCLOCK), on described second bus line, produce data-signal (IMDATA), do not influence the work of described second data processing equipment with the work of controlling described first data processing equipment, and on described first bus line, producing data-signal (II CDATA) during second working method, clocking on described second bus line (II C CLOCK) does not influence the work of described first data processing equipment with the work of controlling described second data processing equipment.

2, equipment as claimed in claim 1 is characterized in that, described control device (CONTROL μ C, 110) comprising:

A microprocessor (CONTROL μ C) produce described data-signal during described first working method, and generation shows that described equipment is the control signal of working or working under described first working method under second working method;

A shift register (112) produces described data-signal during described second working method; With

A traffic pilot (120,130), to be coupled to from the described data-signal of described microprocessor on described second bus line during described first working method according to described control signal, and will be coupled to from the described data-signal of described shift register on described first bus line during described second working method.

3, equipment as claimed in claim 2 is characterized in that, described bus is a serial data bus.

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